Physical Changes

Did you know? Matter is changing around you all the time. Some changes are physical and some are chemical

Do you remember what Physical Properties are??? Color Shape Mass Volume State of Matter Length Magnetism Texture Density

After a PHYSICAL CHANGE, the appearance of the substance may be different but it is still the same substance A physical change does not produce a new substance – molecules are the same

Physical property: States of Matter What does this mean? Only one substance goes into the reaction and one substance comes out. Water  Water Physical property: States of Matter

Cutting a Steak  Steak Steak 

What physical property changed? State of matter Size, shape, mass, volume Is it still the same substance? This is a physical change because before and after being cut the substance is still steak even if the size, shape, and other physical properties changed. It changed from one bigger piece into smaller pieces but no new substance was produced.

Bending Metal Wires  Metal wires Metal wires 

What physical property changed? Shape Why is this a physical change? Bending metal wires is a physical change because a physical change means that no new substance is produced. Although the wires look different they are still the same substance, metal. It just changed shape from flat to bent.

Ice Cream Melting  Ice cream Ice cream 

What physical property changed? State of matter Solid  Liquid Is it still the same substance? This is a physical change because in a physical change the substance stays the same even if it looks different. The only thing that changed about the ice cream is its state of matter (solid to a liquid) but it is still ice cream after it melts.

Exit Ticket A pencil being sharpened Evidence: What physical property changed? Reasoning: Why is this a physical change? 2) Water condensing on your winshield

Breaking glass Glass  Glass What physical property changed? Shape, volume, texture, mass, etc. Is it still the same substance? Yes! Still glass Why? It just changed from one piece to a bunch of smaller pieces

Chemical Properties and Changes

Chemical Properties

Chemical Properties Describes matter based on its ability to change into a new substance with different properties

Chemical Properties These properties can only be observed during a chemical reaction A chemical change has to take place in order to observe them!!!

Chemical Properties Flammability Does it burn? How likely is it to burn?

Flammability Can you think of any substances that are very flammable? Gasoline Paper Wood

Flammability Can you think of any substances that are not flammable? Water

Examples of Chemical Properties What is a reaction? What are some examples of types of reactions? Reactivity

Examples of Reactivity Reacts with oxygen What happens when this substance reacts with oxygen?

Reacting with oxygen Rust! When exposed to oxygen for long periods of time, metal will react with the oxygen to form RUST

Examples of Reactivity Reacts with water What happens to the substance when it interacts with water?

Examples of Reactivity Alka Seltzer and water

Example #1 You light a candle. Flammability or Reactivity? How do you know? It describes the substance’s ability to burn. A candle can burn easily, therefore it is flammable.

Example #2 Vinegar will react with baking soda. Flammability or Reactivity? Reactivity How do you know? Vinegar is reacting with baking soda and carbon dioxide is produced. This describes the interaction between two substances.

Example #3 Yeast acts on sugar to form carbon dioxide and ethanol Flammability or Reactivity? Reactivity How do you know? Yeast is reacting with sugar and forms two new substances, carbon dioxide and ethanol.

Example When charcoal burns in a BBQ grill Reaction between Carbon and Oxygen Provides heat that cooks the dinner and gives off CO2

Chemical Changes

A new substance is formed! After a CHEMICAL CHANGE, a NEW substance is produced with NEW properties. These properties are different from the original substance! A new substance is formed!

Signs that a Chemical Change took place Production of a gas Often appearing as bubbles If it involves FIRE it involves gas (carbon dioxide in the smoke)

Signs that a Chemical Change took place Change in temperature Such as the production or loss of heat

Endothermic reaction A chemical reaction resulting in the loss of heat

Endothermic reaction Example: Ammonium nitrate and water in ice packs

Exothermic reaction Exothermic reaction: A chemical reaction resulting in the production of heat

Exothermic reaction Example Example: Hand warmers Iron reacts with oxygen to produce heat Iron & Oxygen  heat

Signs that a Chemical Change took place New color A chemical reaction results in a color change Metal and oxygen react to form RUST Color changes from silver to brownish red

Signs that a Chemical Change took place Formation of a precipitate An insoluble solid that forms out of a water solution It forms because the solid does not dissolve in water

Example #1: Burning wood

Example #1: Burning wood What chemical property is present? Flamability What is the evidence of a chemical change? Production of a gas (SMOKE) Change in temperature Is it still the same substance? No! Ashes

Example #3: Digestion of Pizza

Example #3: Digestion of Pizza What chemical property is present? Reactivity What is the evidence of a chemical change? New substances with new properties Food is broken down by acid Is it still the same substance? No! Food is broken down into other substances (basic molecule types)

Example #2: Rusting of Metal

Example #2: Rusting of Metal What chemical property is present? Reactivity What is the evidence of a chemical change? Change in color Silver to reddish brown Is it still the same substance? No! Different properties

Physical or Chemical??? Use the A-F cards to separate the Physical Changes from the Chemical Changes! D. Rubbing alcohol evaporates from your hand E. Hydrogen peroxide bubbles when you put it on a cut on your leg F. Your friend melts some butter for her popcorn A. You cut a sheet of aluminum foil in half B. You leave the milk on the counter all night and discover it has soured in the morning C. Your Mom lights a candle in a dark room